I ran into a Spanish forum some time ago, and found an explanation why cables can not alter sound...

The reasoning behind it is that an electrical signal travels with (let`s say, on average), 80% of the speed of light through a conductor. That means that, unless we're talking about really long cables, a waveform in the audible bandwidth, can not do a "full stroke" within the length of a normal sized interlink or a loudspeaker cable, and therefore can not be altered.

Maybe a rather far-fetched explanation, but it somehow seems feasible to me... Any thoughts?

Well, I would hardly call that proof that cables can not alter sound. In general cables do not make an audible difference, but there are other considerations besides the speed of electrical transmission.

A short cable of insufficient cross-sectional area will introduce appreciable resistance, which, combined with the varying inductance with frequency of a speaker will cause a change in the frequency response of the system. If this is considerable, it can be audible.

The length of the cable vs the frequencies of the signal prevents stand waves and similar effects, but that's not the whole story.

Of course quite inexpensive cables have low enough resistance (and inductance at audio frequencies) for them to have no audible effect on the sound.

All real cables have non-zero impedance and can and do alter sound. It is a question of degree. Are the changes audible in the context of other imperfections in the system? For cables of reasonable length and appropriate construction, the answer is generally no.

All real cables have non-zero impedance and can and do alter sound. It is a question of degree. Are the changes audible in the context of other imperfections in the system? For cables of reasonable length and appropriate construction, the answer is generally no.

<nit-picking and elaboration>Cables in themselves do not make sound. They carry electric signals that can be transformed into sound by a loudspeaker. Talking about the sound-altering abilities of a cable can be misleading, as some believe that sound is a perceptual measure just like color is (according to wikipedia, color is, sound it is not). It is fair to say that the behaviour of typical audio-cables connected to typical audio equipment used for typical audio purposes seems to be well understood by "science"*), and that theoretical models fits measurements very well.

When comparing those models/measurements to what we have learned about the human hearing in listening tests, it is hard to understand the fuzz about audio cables. When doing double-blind listening tests, we have been unable to prove that theory and measurements are inadequate. I believe that economical, sociological and psychological models are better able to explain the phenomenon of audiophile cables, but I am not trained in either.

There is still the remote possibility that some small percentage of listeners have super-abilities and that none of them have ever participated in such listening tests. Or that cables somehow affect the subconsciousness in some way that blind listening tests cannot record. Or that existing science was struck by "statistical bad luck" or bad experiment setup. The scientist should always consider the remote possibility of such strange explanations. Only a fool will clutch such straws as evidence that his faith-based conclusion is as good as anything. The practitioner would be well adviced to spend efforts else-where.

-k*)Who gets to decide? The majority of those having a relevant Phd? The one scientist with the most citations within the field? No matter what sensible metric, I am pretty confident of the outcome.

What amazes me is that all the companies that make hi-end loudspeaker-cable, interlinks and power cables actually accomplish this without any design specifications that include the specific audio properties that can be measured (or at least verified in some way) afterwards, let's say in Quality Control.

What amazes me is that all the companies that make hi-end loudspeaker-cable, interlinks and power cables actually accomplish this without any design specifications that include the specific audio properties that can be measured (or at least verified in some way) afterwards, let's say in Quality Control.

Do you see the minute differing design specifications published for brands of gasoline? For toasted oat cereal? 87 octane is 87 octane is 16 gauge copper is 16 gauge copper. Just because something can be measured does not mean it is relevant.

What amazes me is that all the companies that make hi-end loudspeaker-cable, interlinks and power cables actually accomplish this without any design specifications that include the specific audio properties that can be measured (or at least verified in some way) afterwards, let's say in Quality Control.

Just because something can be measured does not mean it is relevant.

...But if the design goal is making a cable that, as close as possible, is capable of transporting an audio signal unmodified (a.k.a. a "better" cable), and there are no known measurements that can actually confirm this behavior, how can a company begin a development process for this?

In other words "Because something can not be measured, it does not mean it is irrelevant" either.

Now I don't know the validity of this measurement and if the findings where reproducible, but a e-shop here in Sweden Fynda has performed a measurement with the same cable in 0.75mm and 2.5mm and as you can see the measurements are not linear with frequency, so the behavior seams to match that of 2Bdecided's explanation.

Considering that one cable has a 0.75mm^2 cross-sectional conductor area (~19 AWG), and the other has 2.5mm (~13 AWG), all this test does is prove the laws of physics correct: less copper = higher resistance/foot, which, in this case, would be easily measurable given the substantial differences in the wire sizes.

A much more interesting/amusing test would be one between two cables from different manufacturers (or maybe better yet, two different "grades" of cables from the same manufacturer) with the same cross-sectional conductor area.

If you're suspecting that it would be flat, a close look should convince you that is not exactly the case. Difference appears to vary by 0.5 dB or so across the measured frequency range. This is caused by complex impedance of the speaker. This is potentially an audible difference even after level match.